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{No Model.) v 2 Sheets-Sheeti. J. M. STEARNS, Jr.

Duplex Telegraph.

No. 243,410. Patented'lunq 28, I881.

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(N0 Modl.) 2 Sheets-Sheet J. M. STEARNS; Jr.

Duplex Telegraph. No. 243,410. Patented June 28,1881.

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UNITED STATES PATENT OFFICE.

J. MILTON STEARNS, JR, OF BROOKLYN, NEW YORK.

DUPLEX TELEGRAPH.

SPECIFICATION forming part of Letters Patent No. 243,410, dated June 28,1881.

Application filed December 30, 1880. (No model.)

To all whom it may concern:

Be it known that I, J. MILTON STEARNS, Jr of the city of Brooklyn, inthe county of Kings and State of New York, have invented an Improvementin Telegraphy, of which the followin g is a specification.

My invention relates particularly to what is known as duplextelegraphing or transmitting messages both ways at the: same time on onewire or single electric circuit, but it also has reference to m ultiplextelegraphin g and optional transmission, or ability at one extremity ofi a single wire to signal and trans- [hit to any one of manylines orcircuits which may be connected to or at the other extremity of saidsingle wire, or work on the same principle at the said point ofjunctionor extremity of said single wire any particular electromagnet.

The object of my invention is to utilize for the specific purposesspecified the common instruments now in use, and to save time andexpense; and the novelty consists in duplex telegraph and multiplextelegraph set up with common instruments in use, and a duplex perfectlyadapted for local stations at will without interfering with the ordinaryinstruments,

all of which tend to cheapen telegraph intercourse.

In the drawings, Figure 1 is a plan of my invention adapted to duplextelegraphing. Fig. 2 is a diagram of arrangement in which the systemshown in Fig. l is adapted to the transmission of twelve messages overthree wires.

Each of the pairs of relays in the multiplex system controls a localcircuit and sounder, (not shown in Fig. 2,) as in the case of the duplexshown in Fig. 1, and operates in precisely the same way, one of saidrelays havinga forward contact and the other a backcontact.

Let there be two terminal stations, XY, connected by a single wire orconductor, L, over which it is desired to establish a duplex system oftelegraphy. At each of said stations is provided a line-battery, N,sufficient to work the line in the usual manner. Each of said ions isprovided with two relays, Aand B, Icy, M, local battery K, and sounderJ. One 0 uch relays, A, so provided is what is called a forward-contactrelay, making contact for a local circuit when its armature is attractedtoward its poles. The other of such relays, B, is what is known as aback-contact relay, or making contact for a local circuit when itsarmature is from or not attracted toward its poles. The line-battery Nof the station being properly set up and connected in series, eitherpole may be, but for convenience of description Iwill sayits'zinc poleis, connected to the earth by wire L, either direct or with the commonconnection for earth of other instruments. The copper pole of saidbattery is connected to the anvil of an ordinary telegraph-key, M, andthe key is connected to one of the terminals or screw-cups of theback-contact relay B. The remaining screw-cup or terminal of saidback-contact relay is connected to one terminal of screw-cup of theforward-contact relay A, and the other terminal or screw-cup of saidforward-contact relay is connected to earth at G through such resistanceas may be required, according to the length and character of the line.On short lines none is necessary. The line-wire L is connected to theconductor joining the two relays, or between saidrelays at any point.The sounder J on one screw-cup or terminal is connected to the localbattery K by wire 1 on one side direct. The other connection from theother terminal or screw-cup of said sounder passes through both theforwardand back contact-points of the said respective relays to theother side of' said local battery.

The apparatus of the other station, Y, is arranged precisely like theone above described, and the line-wire connected in the same relativeplace--to wit, between the two relays of such station. I I

The operation is as follows: The-apparatus being arranged as specified,each main battcry N having zinc poles to ground, and both keys M beingopen, no currents of any kind traverse the line or apparatus. Now closethe key M at X station. Both relays A B at X station draw up theirarmatures, and the current from battery N, passing through 'the key M,passes through both relays A B to the ground G beyond. It will now beseen that, as the local contact F D of the back-contact relay B is drawnapart or broken before the front contact E G of the same local currentor circuit is made, the local circuit is never formed through thesounderJ, and consequently it remains silent, no matter how violentlythe key be worked; but a part of the current passes down the line L tostation Y from the divide between the two relays AB. At Y key M issupposed to be open. Its only path is through the forward-contact relayA at Y station to earth G. This causes that relay to operate itscontact-points E O, and as the backcontact relay B has no magnetism orcurrent in it, the other contact, F D, of the local circuit at Y isalready made, and the full local circuit being made on theforward-contact relay A, the armature of Y sounder J is drawn up andinstantly responds to X key. Thus we see that operating X key keeps itsown. sounder still, while the other or Y sounder responds, and this withY key open. Now shut Ykey. This draws up both its relaysA B, the forwardand back contacts, and its own sounder or local circuit is notformed,.for the reasons stated in relation to the arrangement before.The operation of the sending-key at X station opposes thebattery-current in the back-contact relay BatY station and demagnet-izesit. It falls on and off with the operation of the sending-key M andworks the sounder J, since the front contact on the other relay, A,remains drawn up. Hence it appears that working X key causes Y sounderto go whether Y key is open or shut. If keys at both stations were bothshut at exactly the .same instant of time, it is obvious that theopposed currents would cause the back-contact relays to remaindemagnetized. The forward-contact relays would draw up and the sounderswould both respond-that is, they would attract their armatures andproduce a sound. Suppose we are sending to opposite station, its keybeing closed-that is, we are working its sounder with the back-contactrelay-points thrown off. Now let the opposite orYstation suddenly openits key while the levers of the back-contact relay B are just beginningto move back to make signal. be to hasten the back-contact relay .on itsjourw ney, there now being no current at all in it. As theforward-contact relay A is not in. action at all, opening the key willcause it to fall back, provided the key at the other Y station is open.If shut, no effect or motion is produced. If the other key is open, theresultant effect of the two is to break the sounder or local circuit, asit ought to be,when the opposite key is open, and the break is a point,not a line, as in the case of the make.

It is impossible to contrive any shifting of the keys that would causethe sounders to trip over each other, since in every position they seemto help each other out. Suppose key at Y station is being shut, andbefore that current has time to draw up the relays at home or completethe signal at the other station the other key at X station is suddenlyclosed, a false signal would not be made. The position is one that wouldnot occur probably once .main or line wires.

It is obvious that the only effect will The closing of one key drawsup-the relays at home and the forward-contact relay at the distantstation. Now, while the relay-levers are in transition, in thatinfinitesimal period of time the other key is suddenly shut. The effectwill be to throw the back-contact relay back and help draw up the frontcontact, and the signal is made by the responding of thesounder. Inshort, the sudden closing of the opposite key merely helps a signal intransition to completion in a shorter time, but with no change of form.

To adapt my invention to multiplex telegraphy I merely couple up theapparatus shown in Fig. 1 with one or more sets of the same kind asshown in Fig. 2, in which there are six sending-keys at each station andthree The working of the whole simply depends on keeping therelay-springs adjusted, as'the batteries of each key at one station areof different powers. The actual line-wire of keys 1 is really the threelinewircs. The actual lines of keys 2 and 3 are really two of theIinewires, and of keys 4, 5, and 6 only one ofthe line-wires. Any numberof keys may be arranged in such an apparatus, adding such additionalmain or line wires as become necessary; but it is evident that there areenormous facilities to be had by such an apparatus, for with twelveline-wires one hundred and fifty-six messages may be transmitted overthe wires at the same instant.

I do not confine myself to any particular arrangement of wires, relays,sounders, &c., since my invention has reference, broadly, to duplex andmultiplex telegraphy and repeat ers when arranged for use with front andback contact relays, and without the use of any auxiliary complicatedmechanism, heretofore used.

I am aware of Thompsons patent, No. 195,055, for quadruplex telegraph,of 1877 but it works on an entirely different principle :frornthatherein described, and I claim nothing therein shown or described.

Having now described my invention, what I claim as new, and desire tosecure by Let ters Patent, is-- l. Telegraphic apparatus fortransmittting two messages over a single wire, consisting of the usualline-wire, main batteries, keys, local circuits, sounders, and theirbatteries, combined with two relays capable of making or breaking thesame local circuit, one of said relays being provided with a frontcontact point and the other with a back-contact point, substantially asand for the purpose specified.

2. In a duplex or multiplex telegraph, the line wire or wires, mainbatteries, keys, sounders, local circuits, an d local batteries,combined with two relays located at each of the en f each line-wire, andat the connection or tion of wires connected with two or mo vided with afront contact and the other with a back contact, the armatures of eachpair of said relays working in a local circuit, the backcontact relayalways breaking the local circuit before the front contact relay makesit, unless said relays are rendered inactive by demagnetization, so thatthe sounders in said local circuits shall respond correctly to anyaction of the keys, in the manner and for the purpose specified.

3. In a duplex telegraph, the combination, with line-wire, itsbatteries, and key at either end of said line, of two relays located ateach station in circuit with the line-wire, and provided respectivelywith front and back contact points, the actions of which are regulatedby the currents in the line-wire and govern the local circuits and causethe sounders to respond correctly to the opposite key, substantially inthe manner and for the purpose set forth.

4. In a system of duplex telegraphy, the line-wire, battery, and key,combined with a front-contact relay and a back-contact relay, saidrelays being connected together by a conductor, which, in turn, isconnected to the line- Wire between the relays, the front and backcontact points being in circuit with the sounder and local battery,substantially as shown and described. s

5. In a system of telegraphy, the combination, with the regularline-wire, its batteries, and key, of a front-contact relay, and abackcontact relay, said relays operating on a single local circuit forthe purpose of controlling the action of the sounder, and allowingmessages to be sent over the wire in one or both directions at the sametime, as and for the purpose specified.

In testimony of which invention I hereunto set my hand.

J. MILTON STEARNS, J R. Witnesses:

6120. H. SoNNnBoRN, JAMES F. DOYLE.

